diff --git a/src/network/core/tcp_http.cpp b/src/network/core/tcp_http.cpp
--- a/src/network/core/tcp_http.cpp
+++ b/src/network/core/tcp_http.cpp
@@ -45,7 +45,7 @@ NetworkHTTPSocketHandler::NetworkHTTPSoc
 	size_t bufferSize = strlen(url) + strlen(host) + strlen(GetNetworkRevisionString()) + (data == nullptr ? 0 : strlen(data)) + 128;
 	char *buffer = AllocaM(char, bufferSize);
 
-	DEBUG(net, 5, "[tcp/http] Requesting %s%s", host, url);
+	Debug(net, 5, "[tcp/http] Requesting {}{}", host, url);
 	if (data != nullptr) {
 		seprintf(buffer, buffer + bufferSize - 1, "POST %s HTTP/1.0\r\nHost: %s\r\nUser-Agent: OpenTTD/%s\r\nContent-Type: text/plain\r\nContent-Length: %d\r\n\r\n%s\r\n", url, host, GetNetworkRevisionString(), (int)strlen(data), data);
 	} else {
@@ -86,7 +86,7 @@ void NetworkHTTPSocketHandler::CloseSock
  * Helper to simplify the error handling.
  * @param msg the error message to show.
  */
-#define return_error(msg) { DEBUG(net, 1, msg); return -1; }
+#define return_error(msg) { Debug(net, 1, msg); return -1; }
 
 static const char * const NEWLINE        = "\r\n";             ///< End of line marker
 static const char * const END_OF_HEADER  = "\r\n\r\n";         ///< End of header marker
@@ -142,7 +142,7 @@ int NetworkHTTPSocketHandler::HandleHead
 		 * wrong. You can't have gzips of 0 bytes! */
 		if (len == 0) return_error("[tcp/http] Refusing to download 0 bytes");
 
-		DEBUG(net, 7, "[tcp/http] Downloading %i bytes", len);
+		Debug(net, 7, "[tcp/http] Downloading {} bytes", len);
 		return len;
 	}
 
@@ -155,7 +155,7 @@ int NetworkHTTPSocketHandler::HandleHead
 		/* Search the end of the line. This is safe because the header will
 		 * always end with two newlines. */
 		*strstr(status, NEWLINE) = '\0';
-		DEBUG(net, 1, "[tcp/http] Unhandled status reply %s", status);
+		Debug(net, 1, "[tcp/http] Unhandled status reply {}", status);
 		return -1;
 	}
 
@@ -172,7 +172,7 @@ int NetworkHTTPSocketHandler::HandleHead
 	char *end_of_line = strstr(uri, NEWLINE);
 	*end_of_line = '\0';
 
-	DEBUG(net, 7, "[tcp/http] Redirecting to %s", uri);
+	Debug(net, 7, "[tcp/http] Redirecting to {}", uri);
 
 	int ret = NetworkHTTPSocketHandler::Connect(uri, this->callback, this->data, this->redirect_depth + 1);
 	if (ret != 0) return ret;
@@ -229,7 +229,7 @@ int NetworkHTTPSocketHandler::Receive()
 			NetworkError err = NetworkError::GetLast();
 			if (!err.WouldBlock()) {
 				/* Something went wrong... */
-				if (!err.IsConnectionReset()) DEBUG(net, 0, "Recv failed: %s", err.AsString());
+				if (!err.IsConnectionReset()) Debug(net, 0, "Recv failed: {}", err.AsString());
 				return -1;
 			}
 			/* Connection would block, so stop for now */
@@ -257,7 +257,7 @@ int NetworkHTTPSocketHandler::Receive()
 
 			if (end_of_header == nullptr) {
 				if (read == lengthof(this->recv_buffer)) {
-					DEBUG(net, 1, "[tcp/http] Header too big");
+					Debug(net, 1, "[tcp/http] Header too big");
 					return -1;
 				}
 				this->recv_pos = read;